1. Field of the Invention
The present invention relates to an automobile mirror whereof the angle of incline can be altered by means of remote control, and in particular to a technique for detecting the angle of incline of the mirror.
2. Description of the Prior Art
Generally speaking, the angle of incline of automobile mirrors needs to be adjusted to suit the driver. Since it is very troublesome to perform operations of this sort by hand, various means of adjusting the angle of the mirror by remote control have hitherto been employed.
Adjustment of the mirror angle in this manner is normally achieved by locating sliding rods in suitable positions in the up-down and left-right directions on the rear side of the mirror, and then moving these sliding rods. In other words, the action of moving the sliding rod which is attached in the up-down direction of the mirror causes it to incline upwards or downwards, while moving the sliding rod which is attached in the left-right direction of the mirror causes it to move to the left or to the right. This allows the mirror angle to be adjusted to the desired position by means of remote control.
Since the angle of incline of the mirror normally differs from driver to driver, fine adjustment is required every time the driver changes. Moreover, when a vehicle is being put into a garage, it is convenient for the driver to have the vicinity of the rear wheels of the vehicle within the field of vision. Even so, it is troublesome if the angle of the mirror needs to be adjusted by remote control in order to bring the rear wheels within the field of vision of the mirror whenever the vehicle is being put into a garage. Suggestions have hitherto been made for a mirror position detection device to detect the angle of incline of the mirror. If such a mirror position detection device is coupled to the tilting mechanism of the mirror, it becomes possible to adjust the mirror to the desired angle at a single touch. In other words, where more than one person drives a vehicle, the facility to have a device memorise the mirror angle for each driver allows the angle of incline of the mirror to be adjusted at a single touch to the one best suited to each driver, thus not only making adjustment of the angle very simple, but also making it possible to adjust the angle at a single touch so that the vicinity of the rear wheels can be seen when the vehicle is being put into a garage.
Examples of conventional mirror position detection devices are provided by Japanese Utility Model S57[1982]-157548 (hereinafter referred to as Conventional Example 1) and Japanese Utility Model S58[1983]-115440 (hereinafter referred to as Conventional Example 2). FIG. 12 is an explanatory diagram demonstrating the technical details of the mirror position detection device described in Conventional Example 1. As will be seen from FIG. 12, in this mirror position detection device a contact holder 104 is attached via a link 103 to the trailing edge of an operational shaft 102 which by pushing and pulling serves to tilt the mirror 101. The sliding movement of this contact holder 104 causes the resistance value of a variable resistor 105 to vary, and it is by measuring this resistance value that the angle of incline of the mirror 101 is detected. However, the mirror position detection device described in Conventional Example 1 suffers from the disadvantage that it requires extra space to locate it because the contact holder 104 is attached to the trailing edge of the operational shaft 102, which means that it is impossible to make the whole of the mirror housing more compact.
FIG. 13 is an explanatory diagram demonstrating the technical details of the mirror position detection device described in Conventional Example 2. As is shown in FIG. 13 (A), the sliding movement of a drive shaft 110 causes the mirror to tilt, while a contact 111 slides in line with this along a variable resistor 112. This causes the resistance value of the variable resistor 112 to vary, and it is by measuring this resistance value that the angle of incline of the mirror 101 is detected. Meanwhile, FIG. 13 (B) is a diagram showing the mirror position detection device and the electric equalising circuit. This is configured in such a manner as to detect the voltage level between terminals T10 and T11, which changes with the movement of the drive shaft 110. By detecting this voltage level it is possible to measure the distance which the drive shaft 110 moves, thus allowing the angle of incline of the mirror to be detected. However, the mirror position detection device described in Conventional Example 2 suffers from the same disadvantage as the one described in Conventional Example 1 in that the variable resistor 112 is located on the trailing edge of the drive shaft 110, which means that it is impossible to conserve space.
A further disadvantage is the fact that, as will be seen from FIG. 13 (B), the voltage level which is measured between the terminals T10 and T11 is acquired as a value based on 0 volts. In other words, if the voltage level which is impressed on both ends of the variable resistor 112 is represented as V2, the voltage level between the terminals T10 and T11 is measured in the range 0-V2 volts. The use of a low voltage level close to 0 volts as a detection signal leads to poor accuracy of detection resulting from the effect of noise and other factors, and it is impossible to detect the position with an great degree of accuracy.
Thus, conventional mirror position detection devices are flawed in that the attachment of a variable resistor to the trailing edge of a shaft which serves to tilt the mirror means that they require a large amount of space. Meanwhile, the measurement of voltage levels in a range between 0 and a few volts by connecting a detection contact to a variable resistor which changes according to the angle of incline of the mirror means that it is easily affected by noise and other factors, so that accurate position detection is not possible.
It is an object of the present invention to provide a mirror position detection device which does not require much space for locating its various parts, and which allows the angle of the mirror to be detected with a high degree of accuracy.